Determining parameters of Kerr-Newman black holes by shadow observation from finite distance and spatial infinity

Abstract

We present a method for determining the physical parameters of a Kerr-Newman black hole through shadow observation. In a system comprising a Kerr-Newman black hole, an observer, and a light source, the relevant parameters are mass $M$, specific angular momentum $a$, electric charge $Q$, inclination angle $i$, and distance $r_o$. We consider the cases where the observer is at either a finite distance or spatial infinity. Using our method, the dimensionless parameters $(a/M,Q/M,i)$ can be determined by observing the shadow contour of the Kerr-Newman black hole from spatial infinity. We analytically prove that the shadow contour of the Kerr-Newman black hole observed from spatial infinity is unique, where uniqueness is defined as the absence of two congruent shadow contours for distinct sets of dimensionless parameter values. This method is versatile and can be applied to a range of black hole solutions with charge. Additionally, we show analytically that the shadow contour of a Kerr-Newman black hole observed from a finite distance $r_o$ is not unique, meaning that the parameters of a Kerr-Newman black hole at finite distance cannot be determined from shadow observations. This result reveals a new challenge and provides a clear direction for further research on black hole shadows.

40 pages, 7 figures, sec 5 added, accepted for publication in Classical and Quantum Gravity; Supplemental material is attached. To view the attachment, please download and extract the gzipped tar source file listed under "Other formats''

References in corpus (27)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
• Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A${}^{\ast }$
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
• Measurement of the Kerr Spin Parameter by Observation of a Compact Object's Shadow
• First Sagittarius A* Event Horizon Telescope Results. III: Imaging of the Galactic Center Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multi-wavelength Observations, Data Processing, and Calibration
• First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass
• Constraints on black-hole charges with the 2017 EHT observations of M87*
• Null geodesics and shadow of a rotating black hole in extended Chern-Simons modified gravity
• Shadow of five-dimensional rotating Myers-Perry black hole
• Shadow of a Kaluza-Klein rotating dilaton black hole
• Hidden symmetries, null geodesics, and photon capture in the Sen black hole
• Shape and position of the shadow in the $\delta =2$ Tomimatsu-Sato space-time
• Constraining a modified gravity theory in strong gravitational lensing and black hole shadow observations
• Does the shape of the shadow of a black hole depend on motional status of an observer?
• Null and time-like geodesics in Kerr-Newman black hole exterior
• Image of the Kerr-Newman black hole surrounded by a thin accretion disk
• Constraining Self-interacting Scalar Field Dark Matter From the Black Hole Shadow of the Event Horizon Telescope
• Determining parameters of a spherical black hole with a thin accretion disk by observing its shadow
• Determining parameters of Kerr black holes at finite distance by shadow observation
• Determining parameters of Kerr-Newman black holes by shadow observation from finite distance and spatial infinity

Cited by in corpus (1)

• Determining parameters of Kerr-Newman black holes by shadow observation from finite distance and spatial infinity